1. Field of the Invention
This invention relates to an image recording apparatus for recording images on prescribed recording media using a developer contained in a developer container.
2. Description of Related Art
In conventional image recording apparatuses, a photosensitive drum having a uniformly charged surface thereof is exposed to light to form an electrostatic latent image, thereby attaching toner on portions of the electrostatic latent images using electrostatic force to render the images visible. The visible image attached with the toner is transferred onto the recording medium, and subsequently the toner is fused onto the recording medium when conveyed through a fuser to complete the recording operation. The above described mechanism for attaching the toner to the photosensitive drum is formed as a united body, thereby being detachably attachable to the image recording apparatus, and in some apparatuses, the unused toner container may be provided in a detachably attachable manner. This mechanism is generally referred to as a developing device and serves as a main part for making image forming operation.
In the developing device for attaching the toner to the photosensitive drum, a toner supplying mechanism for supplying the toner from the developer container is installed in the developer container and supplies the toner where the toner inside the developing device is consumed. A roller having indentations, an elastic body, a spiral shaped member, and the like had been used as the supplying mechanism. The developer container also has an agitating mechanism for agitating the developer contained inside the container. The agitating mechanism, moreover, has an agitating member which can rotate upon reception of pushing force from such an electric driving means rotating at prescribed rate and can rotatably fall without reception of driving force from the electric driving means down to a bottom position when reaching at a topmost position. Where the amount of toner remaining in the developer container decreases, this agitating member rotates immediately from the topmost position to the bottom position and remains at the bottom position until pushed by a pushing section formed to a connecting member for connecting the agitating member to the driving means. If toner of a large amount remains, the agitating member rotates slowly from the topmost position to the bottom position due to resistance force of the toner, thereby rotating to the bottom position upon reception of the pushing force from the pushing section. Consequently, the amount of toner remaining inside the developer container can be detected upon measurement of period during which the agitating member remains at the bottom position.
More specifically, Japanese Patent Application Publication No. H11-38,744 has been disclosed as an art for detecting the amount of remaining toner.
For more details, described in Japanese Patent Application Publication No. H11-38,744 is that an agitating shaft composed of a first rectangular convex shaped portion, a second rectangular convex shaped portion, and a rotating shaft is formed in a crank shape so that the first and second rectangular convex shaped portions have a 180-degree difference in phase with respect to the rotating shaft as a center, in which the first and second rectangular convex shaped portions are different from each other in weight and in which the remaining toner amount is detected according to a period during which either the first or second rectangular convex shaped portion is positioned at a bottom position.
However, there raises problem such that the amount of actually remaining toner and the remaining amount of toner detected based on a period during which the agitating member is positioned at the bottom position are not identical to each other due to deviation in the toner profile inside the developer container at a time of supplying operation. For example, the agitating member falls fast from the topmost position to the bottom position and remains at the bottom position for a longer time where the toner is distributed not uniformly despite the remaining toner of a greater amount than a certain ideal value. In such a case, there raises a problem that the supplying operation is undesirably started despite the remaining toner of a greater amount than a certain ideal value, immediately after a controller for controlling the supplying operation confirms that a period during which the agitating member is positioned at the bottom position is shorter than a threshold value. Furthermore, such a trouble such that the detection accuracy for the remaining toner amount deteriorates, is undesirably caused where a period serving as the threshold value is set longer than needed to prevent the above described situation from occurring.
Furthermore, in the above case, deviations may occur in the toner profile and the supplying toner amount, thereby resulting in deviations in the amount of toner remaining inside the developer container caused by the deviations in the amount of supplying toner, where the controller suspends the supplying operation immediately after making a judgment that a period during which the agitating member remains at the bottom position is less than the threshold value. Where the deviations occur in the amount of toner remaining inside the developer container, there raises a problem such that the calculation accuracy is impaired and such that the toner supplying operation is improperly resumed despite the remaining toner of a sufficient amount inside the developer container due to erroneous recognition of the controller with respect to the remaining toner amount.
This invention is made in consideration of the above described background, and it is an object of the invention to provide an image recording apparatus capable of avoiding deterioration in the remaining toner detection accuracy.